As industrial development has increased on a worldwide scale, industrial emissions have become one of the most significant threats to the well-being of the world environment. In an attempt to limit, and even retard, the growth of such emissions, many industrialized countries have passed legislation requiring industries whose emissions are potentially harmful to the environment to take steps to monitor, control, and treat the amount and types of emissions that are released into the environment. Among the most harmful of the industrial wastes are airborne pollutants that may be caused by the burning of fossil fuel, or that may be the byproducts of other processes. Historically, the most common method of xe2x80x9ctreatingxe2x80x9d airborne pollutants has been to allow them to traverse up a smokestack, so that, when released into the atmosphere, they can be dispersed and diluted by the wind and will travel some distance before the heavier particulates return to earth.
A significant part of the United States Environmental Protection Agency""s regulatory efforts are directed at fashioning methods for regulating and reducing noxious gaseous emissions. The first step in regulating gaseous emissions is to determine what substances, and how much of them, are being released through a smokestack or chimney. Traditionally, this task has been performed by using a series of probes that extend into the airflow in a smokestack and that measure air velocity, air temperature, air density, and other measurable parameters. Measurements of these parameters can then be accumulated and processed to provide such information as the chemical composition of various emissions and the amount that is being discharged at any given time.
The present invention is an improved probe in which all of the sensors needed to monitor and assess the amount and types of emissions that may be found within a flowing gaseous discharge are contained within a single device. The probe is suitable for use in a smokestack or other air flume through which a gaseous discharge may be directed. The probe is designed to sample the gases, temperature and flow rates of gas flowing through a smoke stack for the purpose of accurately reporting the pollution content as required by the US EPA under 40 C.F.R. part 75 of the Federal Register.
Traditional systems for obtaining this type of measurement have required at least two separate instruments installed in at least two separate mounting ports or holes in the inner surface of the smokestack. Accordingly, it is an object of this invention to incorporate all instruments needed to obtain gas content, flow rate, and temperature, within a single probe. It is a further object of this invention to provide a means to orient the probe and instruments contained therein in such a manner to obtain the most accurate measurements possible. It is yet another object of this invention to provide an internal means for cleaning the end of the probe so that physical removal and maintenance cleaning of the probe can be minimized or eliminated. It is a further object of this invention to provide signals and gas samples obtained by the probe to remotely-located computerized circuitry for analysis. These and other objects of the invention will become known through the following description of the invention.
The invention combines flow monitoring, temperature measurement, and gas sampling into a single probe. This solves the problem of requiring at least two ports and sometimes three or more ports in the smokestack. Multi ports are not desirable because they weaken the smokestack, and are expensive.
The invention also includes an improved system for orienting a probe within an airflow. Flow monitors require the ability to be positioned and rotated during setup in the field. This is because the accuracy of their measurements depends in large part upon locating the tip of the probe so as to obtain a smooth, laminar flow of gas across the flow monitor. Once a suitable location has been identified, the probe itself must be oriented such that the measuring instruments themselves do not create eddies that would affect the flow monitor. It is desirable for the flow monitor to be oriented such that air velocity is equal on either side of the probe, laterally, and the airstream across the measuring sensor is parallel to the airstream generally within the overall passageway. Where airflow across a flow monitor is variable or eddying, the maximum velocity recorded will not be indicative of the actual velocity of gas within the stack, and inaccuracies in calculated gas volumes and amounts of emissions will lead to errors in corrective measures. In contrast to flow monitors, gas sampling and temperature measurement instruments do not require such precise orientation. The problem of achieving the most desirable orientation is solved by a design that allows the flow measurement device to be rotated around the long axis of the probe and be rotated about its own long axis. The flow monitor is rotated until it reaches a null point, and then is rotated back 90 degrees to assure perfect attitude to the flue gas flow.